Hexafluorocyclobutene is the organofluorine compound with the formula (CF<sub>2</sub>)<sub>2</sub>(CF)<sub>2</sub>. A colorless gas, it is a precursor to a variety of compounds, including squaric acid. Hexafluorocyclobutene is prepared in two steps from chlorotrifluoroethylene. The thermal dimerization gives 1,2-dichloro-1,2,3,3,4,4-hexafluorocyclobutane. Dechlorination of the latter gives hexafluorocyclobutene:
Reminiscent of perfluoroisobutene, hexafluorocyclobutene is quite toxic with an LD = 6000 mg/min/m<sup>âÂÂ3</sup> (mice).